Anionic initiators which contain tertiary amine funtionality have been employed in hydrocarbon solvent polymerizations. Such initiators have the general formula EQU M--Z--N--(C--R.sup.1 R.sup.2 R.sup.3).sub.2
wherein M is defined as an alkali metal selected from lithium, sodium and potassium; Z is defined as a branched or straight chain hydrocarbon connecting group which contains 3-25 carbon atoms; and R.sup.1, R.sup.2 and R.sup.3 are independently defined as hydrogen, alkyl, substituted alkyl groups, aryl or substituted aryl groups. See M. J. Stewart, N. Shepherd, and D. M. Service, Brit. Polym. Jl., 22, 319-325 (1990). However, these amine functional initiators possess low solubility in hydrocarbon solvents (typically less than 0.3 Molar in aliphatic or cycloaliphatic solvents like hexane or cyclohexane). The addition of an ethereal co-solvent does increase the solubility of these initiators; however, this also increases the amount of 1,2-microstructure in the resultatant polymer. See H. L. Hsieh and R. P. Quirk, Anionic Polymerization Principles and Practical Applications, pp. 397-400. Various other techniques have been employed to increase the solubility of these initiators in hydrocarbon solvent. For example, chain extension of the initiator with a conjugated diene increased the solubility several fold. See U.S. Pat. No. 5,527,753.
The facile preparation of alpha, omega-difunctional ("telechelic") polymers has long been sought. These polymers have utility in coatings, adhesives, sealants, asphalt modification, and rocket fuel binders. While progress has been achieved in the synthesis of dihydroxy terminated polymers, the synthesis of diamino terminated polymers remained relatively unexplored.
Nakahama reported the preparation of amino terminated polystyrene by trapping the dianion with an electrophile that contained a protected amine group. A high degree of functionality was achieved by this technique. See K. Ueda, A. Hirao, and S. Nakahama, Macromolecules, 23, 939-945 (1990). However, the reaction conditions (-78.degree. C., THF solvent) were not practical for commercial production of these functionalized polymers.
El-Aasser et al. recently reported the preparation of amino terminated telechelic polybutadiene by a free radical approach. See J. Xu, V. L. Dimonie, E. D. Sudol, and M. S. El-Aasser, Journal of Polymer Science: Part A: Polymer Chemistry, 33, 1353-1359 (1995). Since this is a free radical synthesis, little control of molecular weight, molecular weight distribution, and position of the amine functional group was obtained. Clearly, a reliable, industially applicable synthesis of a telechelic diamine polymer that allows precise control of the molecular architecture is still required.